Permanent magnets are one functional material which is practically indispensable for electronic equipments. The permanent magnets currently in use mainly include alnico magnets, ferrite magnets, rare earth-cobalt (RCo) magnets and more. With remarkable advances in semiconductor devices in recent years, it is increasingly required to miniaturize and upgrade the parts corresponding to hands and feet or mouths (voice output devices) thereof. The permanent magnets used therefor are required to possess high properties, correspondingly.
Although, among permanent magnets, the isotropic permanent magnets are inferior to the anisotropic magnets in certain points in view of performance, the former magnets find good use due to such magnetic properties that no limitation is imposed upon the shape and the direction of magnetization. However, there is much to be desired in performance. The anisotropic magnets rather than the isotropic magnets are generally put to practical use due to high performance. Although the isotropic magnets are substantially formed of the same material as the anisotropic magnets, for instance, alinco magnets, ferrite magnets, MnAl magnets and FeCrCo magnets show a maximum energy product (BH)max of barely 2 MGOe. SmCo magnets broken down into RCo magnets show a relatively high value on the order of 4-5 MGOe, which is nonetheless only 1/4-1/5 times those of the anisotropic magnets. In addition, the SmCo magnets still offer some problems in connection with practicality, since they are very expensive, because samarium Sm which is not abundant is needed, and it is required to use a large amount, i.e., 50-60 weight % of cobalt Co, the supply of which is uncertain.
It has been desired in the art to use relatively abundant light rare earth element such as Ce, Nd and Pr in place of Sm belonging to heavy rare earth and substitute Co with Fe. However, it is well-known that light rare earth and Fe do not give rise to intermetallic compounds suitable for magnets, even when they are mutually melted in a homogeneous state, and crystallized by cooling. Furthermore, an attempt made to strengthen the magnetic force of such light rare earth-Fe alloys was also unsuccessful (see JP Patent Kokai (Laid-Open) Publication No. 57 (1982)-210934, pp.6).
On the other hand, it is known that amorphous alloys based on (Fe, Ni, Co)-R can be obtained by melt-quenching. In particular, it has been proposed (in the aforesaid Publication No. 57-210934) to prepare amorphous ribbons from binary alloys based FeR (as R use is made of Ce, Pr, Nd, Sm, Eu, etc.), especially FeNd and magnetizing the ribbons, whereby magnets are obtained. This process yields magnets having (BH)max of 4-5 MGOe. However, since the resulting ribbons have a thickness ranging from several microns to several tens microns, they should be pressed upon pulverization or laminated in order to obtain magnets of practical bulk. With any existing manners, a lowering of theoretical density and a further lowering of magnetic properties would not be avoided. After all, it is unfeasible to introduce improvements in magnetic properties.